Stable, water-insoluble r-(+)-alpha-lipoic acid salt useful for the treatment of diabetes mellitus and its co-morbidities

ABSTRACT

The present invention relates to oral nutritional and therapeutic products which are useful for preventing or treating compensated and decompensated insulin resistance and associated diseases and sequelae, or diabetes mellitus and its sequelae, complications, and co-morbidities, comprising magnesium R-(+)-alpha-lipoate.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of pending U.S. patentapplication Ser. No. 13/125,724, filed May 11, 2011, which is a nationalphase application under 35 U.S.C. §371 of International PatentApplication No. PCT/US2008/081128, filed on Oct. 24, 2008, whichpublished on Apr. 29, 2010 as Publication No. WO 2010/047717, thecontents of which are hereby incorporated by reference in theirentireties.

FIELD OF THE INVENTION

The present invention relates to oral nutritional and therapeuticproducts which are useful for preventing or treating compensated anddecompensated insulin resistance and associated diseases and sequelae,or diabetes mellitus and its sequelae, complications, andco-morbidities. The pharmaceutical products and methods of the presentinvention are particularly useful in preventing or treating diabetesmellitus and its sequelae, complications, and co-morbidities in humans.

BACKGROUND OF THE INVENTION

Diabetes mellitus (commonly referred to as “diabetes”) is a syndrome ofdisordered metabolism resulting in abnormally high blood sugar levels.Type 2 diabetes mellitus (non-insulin dependent diabetes mellitus) isthe most common form of diabetes and affects 17 million people in theU.S. Late diagnosis, coupled with poor disease management, can result inlong-term complications such as microvascular damage and diseases of theeye, nervous system, and kidney. These complications lead to cataractsand blindness, nerve damage (neuropathy), kidney failure, cardiovasculardisease, and death. The Diabetes Control and Complications trialdemonstrated over 5 years of follow-up study that tight control of bloodglucose is effective in reducing clinical complications significantly.However, trial data showed that even optimal control of blood glucosecould not prevent complications of the disease.

It is known that oxidative stress is causally related to the progressionof diabetes and sequelae, co-morbidities, and complications of thedisease. Oxidative stress is defined in general as excess formationand/or insufficient removal of highly reactive inflammatory species suchas reactive oxygen species (ROS; including, by way of example,superoxide radical anion, hydroxyl radical, peroxyl radicals,hydroperoxyl radicals, hydrogen peroxide, and hypochlorous acid) andreactive nitrogen species (RNS; including, by way of example, nitricoxide, nitrogen dioxide, peroxynitrite, nitrous oxide, and alkylperoxynitrates). Both ROS and RNS are generated under physiologicalconditions; many of these species have physiological activity assignaling molecules and defense mechanisms. However, excess generationof these reactive species, particularly when the excess continues overtime, causes damage to proteins, lipids, and DNA.

Direct evidence of oxidative stress in diabetes is based on studies inwhich markers of oxidative stress, such as plasma and urinaryF2-isoprostane, plasma and tissue levels of nitrotyrosine and superoxideradical anion, and imbalances in physiological anti-oxidants, weremeasured. In diabetes, these markers are generated via non-enzymatic,enzymatic and mitochondrial pathways.

Since anti-oxidants are known to abrogate oxidative stress, a number ofclinical trials have evaluated the beneficial effects of anti-oxidantssuch as vitamin C, vitamin E, and α-lipoic acid on the course ofdiabetes, its sequelae, and co-morbidities. To date, only the resultsfrom clinical studies with α-lipoic acid have supported its clinical useas a treatment for diabetes and its co-morbidities. For example, in theAlpha Lipoic Acid in Diabetic Neuropathy (ALADIN) study, administrationof α-lipoic acid (>600 mg/day) significantly improved patient symptoms.The ALADIN II Study demonstrated that long-term (24 months) use ofα-lipoic acid (600 or 1200 mg daily) improved nerve function. ALADINIII, a randomized multicenter double-blind placebo controlled study,showed that in a cohort of 509 patients, 600 mg α-lipoic acidadministered daily for 6 months improved neuropathy impairment score asearly as 19 days, which was maintained up to 7 months. The DEKAN(Deutsche kardiale autonome neurpathie) study evaluated the effect of800 mg α-lipoic acid or placebo daily in diabetic patients with cardiacautonomic neuropathy for 4 months and showed that heart ratevariability, an indicator of cardiac autonomic neuropathy, significantlyimproved with α-lipoic acid treatment. The SYDNEY trial investigated theeffect of α-lipoic acid treatment on sensory symptoms of diabeticpolyneuropathy as assessed by the Total Symptom Score. Administration ofα-lipoic acid over a 3-week period improved sensory symptoms such aspain, prickling, and numbness. A recent meta-analysis of clinical trialswith α-lipoic acid concluded that treatment with α-lipoic acid (600mg/day) over a 3-week period is safe and effective in improving positiveneuropathic symptoms as well as neuropathic deficits. [J. S. Johansen,A. K. Harris, D. J. Rychly, and A. Ergul, “Oxidative stress and the useof antioxidants in diabetes: Linking basic science to clinicalpractice,” Cardiovasc Diabetol 2005; 4:5, and references therein]

α-Lipoic acid is the common name for the chiral compound1,2-dithiocyclopentane-3-valeric acid. α-Lipoic acid is availablecommercially as both the racemic mixture, RS-α-lipoic acid (alsocommonly known as thioctic acid), and as the single enantiomer,R-(+)-α-lipoic acid. All of the clinical studies presented above usedRS-α-lipoic acid.

R-(+)-α-lipoic acid is the form of α-lipoic acid found in the body.Lysine-bound R-(+)-α-lipoate is a coenzyme of α-ketoacid dehydrogenases(pyruvate dehydrogenase, α-ketoglutarate dehydrogenase, etc.) and actsat a key site in the sugar and energy metabolism of the cell. Inaddition, R-(+)-α-lipoate functions as a physiological redox system andis reduced intracellularly to its corresponding R-(+)-α-dihydrolipoate,which is subsequently re-oxidized, both intra- and extra-cellularly, toR-(+)-α-lipoate. Dihydrolipoate is able to regenerate otheranti-oxidants such as vitamin C, vitamin E, and reduced glutathionethrough redox cycling.

It is well known that the pharmacological properties of the twoenantiomers of α-lipoic acid differ with respect to their physiologicalactivities. By way of example, U.S. Pat. Nos. 5,693,664, 5,948,810,6,284,787, and U.S. Patent Application Publication No. US 2008/0095741(all to Wessel et al.) disclose that R-(+)-α-lipoic acid, itswater-soluble salts, its esters, and its amides are more suitable forthe prevention and treatment of diabetes and its complications than arethe enantiomeric S-(−)-α-lipoic acid, its water-soluble salts, itsesters, and its amides. (The water-soluble salts disclosed by Wesselinclude salts of organic amines, such as α-methylbenzylamine,diphenylamine, trometamol, and 2-amino-2-hydroxymethyl-1,3-propyleneglycol.) For example, glucose assimilation was stimulated by theR-enantiomer of lipoic acid by a factor greater than 2, comparable tothe effect of 200 nM insulin, whereas the S-enantiomer effected littleor no change. Likewise, R-(+)-α-lipoate stimulated the translocation ofglucose transporters (GLUT 1 and GLUT 4) from the cytosol to the plasmamembrane; S-(−)-α-lipoate had no effect or has an inhibiting effect andappeared to lower the total content of glucose transporters. Further,the activity of a key enzyme involved in glucose metabolism, pyruvatedehydrogenase, was increased by R-(+)-α-lipoate but inhibited byS-(−)-α-lipoate.

It is also known that RS-α-lipoic acid is more stable thanR-(+)-α-lipoic acid. RS-α-Lipoic acid may be stored in a closed andsealed amber container at room temperature for a year or longer. Incontrast, R-(+)-α-lipoic acid must be stored in a closed and sealedamber container at refrigerated temperatures and must be used within afew months, since it gradually polymerizes to intractable polymers anddegrades to physiologically and therapeutically inactive compounds byloss of sulfur-containing compounds.

Further, it is known that adequate magnesium is essential forglycolysis, formation of adenosine-3″,5″-cyclic monophosphate,energy-dependent membrane transport, and over 300 other enzymeprocesses. Magnesium plays the role of a second messenger for insulinaction. Conditions associated with insulin resistance (i.e., reducedsensitivity to the activity of insulin), such as diabetes, hypertensionor aging, are also associated with low intracellular magnesium contents.In diabetes mellitus, low intracellular magnesium levels have beenreported, likely as a result from both increased urinary losses andinsulin resistance. Chronic magnesium supplementation can contribute toan improvement in both islet beta-cell response and insulin action innon-insulin-dependent diabetic subjects.

Therefore, a significant, unmet need exists for provision of a stabledrug for preventing or treating diabetes mellitus and sequelae,complications, and co-morbidities. If that stable drug containedmagnesium, the properties of magnesium disclosed above indicate that thestable, magnesium-containing drug would provide additive therapeuticbenefits to those suffering from metabolic disorders related todisordered glycolysis. The present invention addresses this unmet needby providing a stable magnesium-containing drug.

SUMMARY OF THE INVENTION

The present invention is an oral nutritional and therapeutic compositionuseful for preventing or treating diabetes mellitus and its sequelae,complications, and co-morbidities, comprising a unit dosage or servingof magnesium R-(+)-alpha-lipoate. A method of preventing or treatingdiabetes mellitus, its sequelae, complications, and co-morbidities in ahuman, comprising administering to said human a safe and effectiveamount of a supplement comprising magnesium R-(+)-alpha-lipoate, is alsodisclosed. Further, a method of preventing and treating diabetesmellitus, its sequelae, complications, and co-morbidities in awarm-blooded animal with a therapeutically effective amount of apharmaceutical composition comprising magnesium R-(+)-alpha-lipoate isdisclosed. A method of preparing magnesium R-(+)-alpha-lipoate is alsoprovided. In some embodiments, the present invention comprises use ofmagnesium R-(+)-alpha-lipoate in the manufacture of a medicament for theprevention or treatment of compensated and decompensated insulinresistance and associated diseases and sequelae, or diabetes mellitusand its sequelae, complications, and co-morbidities.

Other features, advantages, and embodiments of the invention will beapparent to those of ordinary skill in the art from the followingdescription, examples, and appended claims.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing the percentage of bioavailable magnesium inmagnesium R-(+)-alpha-lipoate (Mg RALA) at each value of pH in the rangefrom pH 4 to pH 8, the pH range of the human gastrointestinal tract.

FIG. 2 is a chromatogram showing the relative retention times ofR-(+)-alpha-lipoate of the invention and S-(−)-alpha-lipoate. Therelative peak heights confirm that R-(+)-alpha-lipoate of the inventionhas at least 95% chiral purity.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is an oral nutritional and therapeutic compositionuseful for the treatment of diabetes mellitus and its sequelae,co-morbidities, and complications, comprising a unit dosage or servingof magnesium R-(+)-alpha-lipoate. This agent promotes the assimilationof blood sugar in the tissue. This activity is of clinical relevance inthe case of pathological disorders of the control of blood sugaradjustment, as in the case of diabetes mellitus types I and II, or inthe case of disorders in insulin sensitivity of the tissue (insulinresistance). This applies in the case of monotherapy, as well as in thecase of a combination with other drugs for the treatment of diabetesmellitus or of insulin resistance, such as oral anti-diabetic drugs and,in particular, insulin. Furthermore, complications, sequelae, orco-morbidities of diabetes mellitus or of insulin resistance can also beaffected therapeutically by the treatment of the basic diseases with thestable drug of this invention. The composition is useful in men andwomen.

The present invention also relates to a method of treating compensatedand decompensated insulin resistance and, with that, of associateddiseases and sequelae, or of diabetes mellitus and its sequelae andcomplications in a human, comprising administering to said human a safeand effective amount of a supplement comprising an effective amount ofmagnesium R-(+)-alpha-lipoate.

In addition, the present invention relates to a method of preventing andtreating compensated and decompensated insulin resistance and, withthat, of associated diseases and sequelae, or of diabetes mellitus andits sequelae and complications in a warm-blooded animal with atherapeutically effective amount of a pharmaceutical compositioncomprising pharmaceutical quality magnesium R-(+)-alpha-lipoate.Included within the scope of this invention is a method of preventingand treating compensated and decompensated insulin resistance and, withthat, of associated diseases and sequelae, or of diabetes mellitus andits sequelae and complications in a warm-blooded animal using oralpharmaceutical compositions comprising pharmaceutical quality magnesiumR-(+)-alpha-lipoate and a suitable pharmaceutical carrier.

Magnesium R-(+)-alpha-lipoate is the magnesium salt of R-(+)-α-lipoicacid. Magnesium R-(+)-α-lipoate is a stable, non-hygroscopic, lightyellow powder having a molecular formula of Mg(C₈H₁₃O₂S₂)₂, the generalformula

and a molecular weight of 434.94. Pharmaceutical quality magnesiumR-(+)-alpha-lipoate of this invention has at least about 95% chiralpurity. In other words, pharmaceutical quality magnesiumR-(+)-alpha-lipoate of the invention contains less than about 5% ofmagnesium S-(−)-alpha-lipoate.

Magnesium R-(+)-α-lipoate has been selected because this stable saltprovides both magnesium and R-(+)-alpha-lipoate, the anion ofR-(+)-alpha-lipoic acid. R-(+)-α-Lipoate is the form of alpha-lipoicacid naturally found in the human body. Further, R-(+)-alpha-lipoate isa widely distributed physiological antioxidant that combines freeradical scavenging properties with an ability, after intracellularreduction to dihydrolipoic acid, to regenerate the levels of othernonenzymatic and enzymatic antioxidants, including glutathione (GSH),ascorbate, α-tocopherol, catalase and GSH peroxidase. The physiologicalform of R-(+)-α-lipoate, the R-(+)-enantiomer, is present in alleukaryotic and prokaryotic cells. R-(+)-α-Lipoate has demonstratedsafety and an absence of toxicity when administered chronically tohumans. Magnesium is the fourth most prevalent element in the body andthe second most abundant intracellular ion. Since magnesium is acofactor in over 300 enzyme systems, adequate magnesium is essential formany biosynthetic processes, including, by way of example, glycolysis,formation of adenosine-3″,5″-cyclic monophosphate, energy-dependentmembrane transport, and transmission of the genetic code. Therelationship between insulin and magnesium has been recently studied byPaolisso et al. [G. Paolisso, A. Scheen, F. D'Onofrio, and P. Lefebvre,Magnesium and glucose homeostasis. Diabetologia 1990; 33(9): 511-514.]These studies showed that magnesium plays the role of a second messengerfor insulin action. Conversely, insulin itself was shown to be animportant regulatory factor of intracellular magnesium accumulation. Theauthors reported that conditions associated with insulin resistance,such as hypertension or aging, are also associated with lowintracellular magnesium contents. In diabetes mellitus, lowintracellular magnesium levels have been reported, likely as a resultfrom both increased urinary losses and insulin resistance. The extent towhich such a low intracellular magnesium content contributes to thedevelopment of macro- and microangiopathy co-morbidities of diabetesremains to be established. A reduced intracellular magnesium content hasbeen reported to contribute to the impaired insulin response and actionwhich occurs in Type 2 (non-insulin-dependent) diabetes mellitus.Chronic magnesium supplementation contributes to an improvement in bothislet beta-cell response and insulin action in non-insulin-dependentdiabetic subjects.

In general, compensated insulin resistance implies long-standing andadequate control of blood glucose levels as manifested by glycosylatedhemoglobin (HbA1c) levels (a simple and routine blood test) withinnormal levels, i.e., <about 7.0%. This is an index of metabolic controlover several months that doctors use as an index of how well a patientis balancing diet, medications (insulin, etc.), exercise and othervariables, i.e., how well “compensated” they are with their diabetes.)Poorly compensated insulin resistance (levels of Hb1Ac higher than about7.0%) is associated with retinopathy, nephropathy, neuropathy,vasculopathy, etc.

The term “bioavailability” refers to the amount of a substance that isabsorbed in the intestines and ultimately available for biologicalactivity in a subject's cells and tissues.

The term “excipient material” is intended to mean any compound forming apart of the formulation which is not intended to have biologicalactivity itself and which is added to a formulation to provide specificcharacteristics to the dosage form, including by way of example,providing protection to the active ingredient from chemical degradation,facilitating release of a tablet or caplet from equipment in which it isformed, and so forth.

By the terms “treating” and “treatment” and the like are used herein togenerally mean obtaining a desired pharmacological and physiologicaleffect. The effect may be prophylactic in terms of preventing orpartially preventing a disease, symptom or condition thereof and/or maybe therapeutic in terms of a partial or complete cure of a disease,condition, symptom or adverse effect attributed to the disease. The term“treatment” as used herein encompasses any treatment of a disease in amammal, particularly a human and includes: (a) preventing the diseasefrom occurring in a subject which may be predisposed to the disease buthas not yet been diagnosed as having it; (b) inhibiting the disease orarresting its development; (c) relieving the disease, causing regressionof the disease and/or its symptoms or conditions; or (d) returning aclinical value to the concentration range normally found in a subject.

The phrase “pharmaceutical quality” means that magnesiumR-(+)-alpha-lipoate has a purity of at least about 90% and a chiralpurity of at least about 90%. In addition, magnesium R-(+)-alpha-lipoatecontains at most low part per million quantities of contaminating metalshaving known toxicities in humans. Examples of such metals includealuminum, lead, thallium, arsenic, barium, cadmium, and so forth.

The phrase “therapeutically effective” is intended to qualify the amountof magnesium R-(+)-alpha-lipoate for use in the orally administeredcomposition of this invention which will achieve the goal of providingthe quantity of R-(+)-alpha-lipoate and magnesium that are needed toprevent and treat compensated and decompensated insulin resistance and,with that, of associated diseases and sequelae, or of diabetes mellitusand its sequelae and complications in a warm-blooded animal.

For the purpose of this disclosure, a warm-blooded animal is a member ofthe animal kingdom which includes but is not limited to mammals andbirds. The most preferred mammal of this invention is human.

To provide a more concise description, some of the quantitativeexpressions given herein are not qualified with the term “about.” It isunderstood that whether the term “about” is used explicitly or not,every quantity give herein is meant to refer to the actual given value,and it is also meant to refer to the approximation to such given valuethat would reasonably be inferred based on the ordinary skill in theart, including approximations due to the experimental and/or measurementconditions for such given value.

Magnesium R-(+)-alpha-lipoate is not commercially available. In order toobtain sufficient quantities of this salt for use in this invention, amethod of preparing pharmaceutical quality magnesium R-(+)-alpha-lipoatewas required.

A method of preparing magnesium alpha-lipoate was disclosed by Pearsonand Richardson in U.S. Pat. No. 6,288,106 B1. By this method, Pearsonand Richardson disclose that a solution of alpha-lipoic acid inanhydrous ethanol was added with stirring to a solution of magnesiumethoxide in anhydrous ethanol. After stirring the reaction mixture for30 minutes, the solvent was evaporated under reduced pressure to affordthe magnesium salt of alpha-lipoic acid. Attempts to preparepharmaceutical quality magnesium R-(+)-alpha-lipoate by the method ofPearson and Richardson failed. After evaporation of the solvents, asrequired by the method of Pearson and Richardson, a stringy, intractablepolymer was obtained; no pharmaceutical quality magnesiumR-(+)-alpha-lipoate was isolated. R-(+)-α-Lipoic acid is a hydrophobicfatty acid that is known to undergo self-polymerization by heat- orlight-induced cleavage of the sulfur-sulfur bond on one molecule to anunstable diradical that can interact with a second lipoic acid moleculeat its sulfur-sulfur bond to generate a new ring-opened dimer of lipoicacid. This polymerization process can be repeated multiple times togenerate polylipoates (i.e., polymers of ring-opened lipoic acid) ofvarying sizes and molecular weights. Monomeric R-(+)-alpha-lipoic acidis a yellow powder which is soluble in organic solvents such asalcohols, alkanes, etc. In contrast, the polylipoates are intractable,“gummy” yellow solids which adhere to the surfaces of containers and areessentially insoluble in aqueous or organic solvents.

Therefore, a synthesis of pharmaceutical quality magnesiumR-(+)-alpha-lipoate was required which provided a powdery solid at roomtemperature without a requirement for evaporation of solvents or lengthyexposure to heating, wherein the solid had a purity of at least about90% and a chiral purity of at least about 90% and within ±5% of thechiral purity of the R-(+)-alpha-lipoic acid starting material used forits preparation. R-(+)-alpha-Lipoic acid is an acid; a magnesium salt ofan acid is obtained by reaction of the acid with a magnesium-containingbase. To meet the additional criterion that the chiral purity of themagnesium R-(+)-alpha-lipoate equals the chiral purity of theR-(+)-alpha-lipoic acid starting material used for its preparation, theacid-base reaction must occur under conditions which are non-racemizing.

Magnesium hydroxide and magnesium oxide are commercially available basescontaining magnesium. Both of these bases are insoluble in water ororganic solvents. Because of this lack of solubility, reaction ofmagnesium hydroxide or magnesium oxide with R-(+)-alpha-lipoic acid doesnot occur under commercially useful conditions.

Magnesium methoxide, magnesium ethoxide, magnesium t-butoxide, andmagnesium acetylacetonate are bases containing magnesium. A solution ofmagnesium methoxide in methanol is commercially available. A solution ofmagnesium ethoxide in ethanol can be prepared if 70 mL or more ofethanol per gram of magnesium ethoxide is heated. The inventorsdiscovered that solutions of magnesium t-butoxide or magnesiumacetylacetonate can be prepared in methanol or acetonitrile at roomtemperature.

Lipoic acid in solution is known to be susceptible to undesirableoxidation reactions. R-(+)-alpha-Lipoic acid in solution is verysusceptible to oxidation by oxygen in air, particularly in the presenceof a base. The inventors discovered that oxidation is prevented bypreparing solutions of R-(+)-alpha-Lipoic acid in an inert atmosphere ofnitrogen or argon and completing subsequent reactions under theseconditions.

The inventors studied the reaction of 2 mole equivalents ofR-(+)-alpha-lipoic acid with one mole equivalent of magnesium as amagnesium alkoxide. All reactions were carried out under an inertatmosphere and in subdued light, since these conditions preventedundesirable oxidation and/or polymerization. When a solution ofmagnesium ethoxide in ethanol was added to a solution ofR-(+)-alpha-lipoic acid in ethanol, the volumes of ethanol that wererequired to obtain a solution of magnesium ethoxide at room temperaturewere too large to be commercially practical and the desired product,magnesium R-(+)-alpha-lipoate, failed to precipitate from solution. Whena solution of magnesium ethoxide in methanol was added to a solution ofR-(+)-alpha-lipoic acid in methanol or ethanol, the desired product,magnesium R-(+)-alpha-lipoate failed to precipitate from solution. Whena solution of magnesium methoxide in methanol was added to a solution ofR-(+)-alpha-lipoic acid in methanol or ethanol, the desired product,magnesium R-(+)-alpha-lipoate failed to precipitate from solution. Ifacetone was then added to induce precipitation, a glassy green solid wasobtained that was not magnesium R-(+)-alpha-lipoate.

When a solution of magnesium acetylacetonate in methanol was added to asolution of R-(+)-alpha-lipoic acid in isopropanol, acetonitrile, ormethanol/isopropanol, the desired product, magnesium R-(+)-alpha-lipoatewas not obtained. Instead, a mixed salt, magnesium(R-(+)-alpha-lipoate)(acetylacetonate), was obtained.

After lengthy experimentation, the inventors discovered conditions forthe preparation of magnesium R-(+)-alpha-lipoate, a powdery yellowsolid. When a solution of magnesium methoxide in methanol was added to asolution of R-(+)-alpha-lipoic acid in isopropanol, acetonitrile, ormethanol/isopropanol, the desired product, magnesium R-(+)-alpha-lipoatewas obtained. Likewise, when a solution of magnesium t-butoxide inmethanol was added to a solution of R-(+)-alpha-lipoic acid inisopropanol, acetonitrile, or methanol/isopropanol, the desired product,magnesium R-(+)-alpha-lipoate was obtained, but the yield was lower.

Under optimal conditions, the inventors discovered that the dropwiseaddition of a solution of magnesium methoxide in methanol to a clearsolution of R-(+)-alpha-lipoic acid in methanol-isopropyl alcoholsolution maintained under an inert atmosphere of nitrogen or argon andshielded from light provided magnesium R-(+)-alpha-lipoate as a solid,pale yellow precipitate. The volume ratios of solvent that were used inthis preparation were from 25-35 milliliters isopropyl alcohol for eachgram of R-(+)-alpha-lipoic acid and from 5-15 milliliters methanol foreach gram of R-(+)-alpha-lipoic acid. (The volume of methanol that wasused was provided by the magnesium methoxide solution and bysupplemental methanol.) Magnesium R-(+)-α-lipoate was isolated byfiltration and purified from contaminants by washing with freshisopropyl alcohol. Magnesium R-(+)-α-lipoate did not melt attemperatures below 300° C. Analysis for magnesium content by titrationshowed that the magnesium content was about 5.6% by weight, as expected.Analysis for R-(+)-α-lipoate content by HPLC showed that theR-(+)-α-lipoate was about 95% by weight, as expected. HPLC analysis alsoconfirmed that the chiral purity was greater than 95%, within ±5% of the96% chiral purity of the R-(+)-alpha-lipoic acid starting material usedfor its preparation, an observation that confirmed that no racemizationoccurred during reaction. Analysis of trace metals by inductivelycoupled plasma mass spectrometry showed that magnesium R-(+)-α-lipoatecontained only very low parts per million levels of toxic metals, suchas aluminum, tin, arsenic, barium, lead, and thallium. Thus, this newlydiscovered method of preparing pharmaceutical quality magnesiumR-(+)-α-lipoate uses inexpensive, commercially available reagents,reaction conditions that are easily scaled to commercial quantities,comprises reaction conditions that are non-racemizing, and providesgreater than 65% yields of magnesium R-(+)-α-lipoate of greater than 95%purity and greater than 95% chiral purity.

Pharmaceutical quality magnesium R-(+)-α-lipoate that is prepared in themanner disclosed above is a stable magnesium salt of R-(+)-α-lipoicacid. We studied the stability of magnesium R-(+)-α-lipoate of thepresent invention during storage at ambient temperatures for a period oftwo years and found that the physical state and chemical properties ofthe salt did not change over time. The salt was not hygroscopic. Thispale yellow salt had no characteristic odor or taste.

Magnesium R-(+)-alpha-lipoate is insoluble in water, a property thatconventionally indicates that this salt has poor bioavailability.However, the inventor has found that both magnesium and R-(+)-α-lipoateions are available from suspensions of the salt in aqueous solutionshaving a pH in the range from about 4 to about 8. This is the pH rangethat is found in parts of the human gastrointestinal system, where a pHof 4 is found in the stomach after food has been ingested, a pH of 6-7is found in the upper intestine, and a pH of 8 is found in the lowerintestine. R-(+)-α-Lipoate has both hydrophilic and lipophilicproperties. Based on this combination properties, it is chemicallyreasonable to expect that R-(+)-α-lipoate binds to lipophilic membranes,as are found on cells throughout the body, and is taken up, at least inpart, by absorption of magnesium-bound lipoate from the gastrointestinaltract. Thus, its bioavailability is unexpectedly high, as compared toconventional, water-insoluble magnesium salts.

A unit dose or serving of a composition of the invention provides from 5mg to about 100 mg magnesium, on an elemental basis, and from 95 mg toabout 1,900 mg of R-(+)-α-lipoate in the form of pharmaceutical qualitymagnesium R-(+)-alpha-lipoate. A clinician has the training andexpertise to determine which dose level and related dosage regimen aremost appropriate for a patient.

The compositions of this invention can be administered by any means thateffects contact of the active ingredients with the site of action in thebody of a warm-blooded animal. A most preferred means of administrationis by the oral route (i.e., ingestion). The compositions of thisinvention can be administered one or more times each day, so as tofacilitate and enhance compliance with dosage regimens.

The active ingredients can be administered by the oral route in soliddosage forms, such as tablets, capsules, and powders, or in liquiddosage forms, such as elixirs, syrups, and suspensions. Thepharmaceutical composition is preferably made in the form of a dosageunit containing a particular amount of each active ingredient. One mostpreferred oral dosage form of a composition of the present invention isan admixture of powders contained within a sachet. Because a compositionof the present invention is not hygroscopic and has no repugnant tasteor odor, the admixture of powders comprising a composition of thepresent invention can be sprinkled on food or stirred into beverages toenhance ease of use and support high levels of compliance with dailydosage regimens.

In general, the pharmaceutical dosage forms of compositions of thisinvention can be prepared by conventional techniques, as are describedin Remington's Pharmaceutical Sciences, a standard reference in thisfield [Gennaro A R, Ed. Remington: The Science and Practice of Pharmacy.20^(th) Edition. Baltimore: Lippincott, Williams & Williams, 2000]. Fortherapeutic purposes, the active components of this combination therapyinvention are ordinarily combined with one or more adjuvants appropriateto the indicated route of administration. If administered per os, thecomponents may be admixed with lactose, sucrose, starch powder,cellulose esters of alkanoic acids, cellulose alkyl esters, talc,stearic acid, magnesium stearate, gelatin, acacia gum, sodium alginate,polyvinylpyrrolidone, and/or polyvinyl alcohol, and then tabletted orencapsulated for convenient administration. Such capsules or tablets maycontain a controlled-release formulation as may be provided in adispersion of active compound in hydroxypropyl methylcellulose. Soliddosage forms can be manufactured as sustained release products toprovide for continuous release of medication over a period of hours.Compressed tablets can be sugar coated or film coated to mask anyunpleasant taste and protect the tablet from the atmosphere, or entericcoated for selective disintegration in the gastrointestinal tract. Boththe solid and liquid oral dosage forms can contain coloring andflavoring to increase patient acceptance. Other adjuvants and modes ofadministration are well and widely known in the pharmaceutical art.

Dosing for oral administration may be with a regimen calling for singledaily dose, or for a single dose every other day, or for multiple,spaced doses throughout the day. The active agents which make up thetherapy may be administered simultaneously, either in a combined dosageform or in separate dosage forms intended for substantially simultaneousoral administration. The active agents which make up the therapy mayalso be administered sequentially, with either active component beingadministered by a regimen calling for two-step ingestion. Thus, aregimen may call for sequential administration of the active agents withspaced-apart ingestion of the separate, active agents. The time periodbetween the multiple ingestion steps may range from a few minutes toseveral hours, depending upon the properties of each active agent such apotency, solubility, bioavailability, plasma half-life and kineticprofile of the agent, as well as depending upon the age and condition ofthe patient. The active agents of the therapy whether administeredsimultaneously, substantially simultaneously, or sequentially, mayinvolve a regimen calling for administration of one active agent by oralroute and the other active agent by intravenous route. Whether theactive agents of the therapy are administered by oral or intravenousroute, separately or together, each such active agent will be containedin a suitable pharmaceutical formulation of pharmaceutically-acceptableexcipients, diluents or other formulations components.

EXAMPLE 1 Preparation and Analysis of Pharmaceutical Quality MagnesiumR-(+)-Alpha-Lipoate

A. Attempted methods of preparing magnesium R-(+)-alpha-lipoate. Sevendifferent reactions were carried out repetitively in an attempt toprepare magnesium R-(+)-alpha-lipoate (Table 1). Each product wasanalyzed for magnesium content by titration with eriochrome black andfor R-(+)-alpha-lipoate content by HPLC.

TABLE 1 Attempted methods of preparing magnesium R-(+)-alpha-lipoateR-(+)-alpha- Rx. Lipoic Acid Mg Reagent Conditions Result AR-(+)-α-lipoic 1 equivalent of Reaction at Evaporation of the solvent,as acid; 2 magnesium room disclosed in U.S. Pat. No. equivalentsethoxide in temperature 6,288,106, left a stringy, dissolved inanhydrous ethanol intractable polymeric gum that anhydrous could not bedissolved in water, ethanol organic solvents, or acids. Analyticalresults indicated that the product was not magnesiumR-(+)-alpha-lipoate. B R-(+)-α-lipoic 1 equivalent of Reaction at Agreen solid precipitated and was acid; 2 magnesium room isolated byfiltration. The solid equivalents methoxide in temperature could not bedissolved in water, dissolved in anhydrous organic solvents, or acids.acetone methanol Analytical results indicated that the product was notmagnesium R-(+)-alpha-lipoate. C R-(+)-α-lipoic 1 equivalent of Reactionat No solid precipitated from the acid; 2 magnesium room reaction.equivalents methoxide in temperature dissolved in anhydrous methanolmethanol D R-(+)-α-lipoic 1 equivalent of Reaction at No solidprecipitated from the acid; 2 magnesium room reaction equivalentsmethoxide in temperature dissolved in anhydrous ethanol methanol ER-(+)-α-lipoic 1 equivalent of Reaction at A mixture of green solid andacid; 2 magnesium room yellow-green solid precipitated equivalentsmethoxide in temperature and was isolated by filtration. The dissolvedin anhydrous solids did not completely dissolve acetonitrile methanol inorganic solvents or acids. Analytical results indicated that the productwas not magnesium R-(+)-alpha-lipoate. F R-(+)-α-lipoic 1 equivalent ofReaction at A pale yellow solid precipitated acid; 2 magnesium t- roomand was isolated by filtration. The equivalents butoxide in temperatureyield of product was about 50% of dissolved in anhydrous theoretical.Analytical results isopropyl ethanol/acetonitrile indicated that theproduct was alcohol magnesium R-(+)-alpha-lipoate. G R-(+)-α-lipoic 1equivalent of Reaction at A pale yellow solid precipitated acid; 2magnesium room and was isolated by filtration. equivalentsacetylacetonate in temperature Analytical results indicated thatdissolved in anhydrous the product was magnesium acetonitrile methanolmono-R-(+)-alpha-lipoate mono- acetylacetonate.

B. Method of Preparation of pharmaceutical Quality magnesiumR-(+)-alpha-lipoate of this invention. Dropwise addition of 485 mL of asolution of magnesium methoxide in methanol (a volume equivalent toabout one mole of magnesium methoxide) to a clear solution of about 100g of R-(+)-alpha-lipoic acid (2 mole equivalents) having a chiral purityof about 96% in 3,500 mL of methanol-isopropyl alcohol solutionmaintained under an inert gas and shielded from light provided magnesiumR-(+)-alpha-lipoate as a solid, pale yellow precipitate. MagnesiumR-(+)-α-lipoate was isolated by filtration and purified fromcontaminants by washing with fresh isopropyl alcohol. MagnesiumR-(+)-α-lipoate did not melt at temperatures below 300° C. Analysis formagnesium content by titration showed that the magnesium content was5.6% by weight, as expected. Analysis for R-(+)-α-lipoate content byHPLC showed that the R-(+)-α-lipoate was 94.4% by weight, as expected.HPLC analysis by a method useful for the determination of chiral purityconfirmed that the magnesium R-(+)-alpha-lipoate obtained therefrom hadat least about 95% chiral purity; thus, no racemization occurred duringits preparation. Analysis of trace metals by inductively coupled plasmamass spectrometry showed that magnesium R-(+)-α-lipoate contained onlyvery low parts per million levels of toxic metals, such as aluminum,tin, arsenic, barium, lead, and thallium. Thus, pharmaceutical qualitymagnesium R-(+)-α-lipoate was obtained in greater than 65% yields andhad greater than 95% purity and greater than 95% chiral purity.

EXAMPLE 2 Stability of Magnesium R-(+)-Alpha-Lipoate of this Invention

Samples of the magnesium R-(+)-α-lipoate of Example 1.B. were stored atroom temperature. Test samples of magnesium R-(+)-α-lipoate were exposedto ambient environments with relative humidities as high as 75% for aperiod of a week. The physical appearance and properties of the compounddid not change during storage. The data indicated that the compound wasnot hygroscopic and was stable during storage under these conditions.Test samples of magnesium R-(+)-α-lipoate were stored at ambienttemperatures for two years. The physical appearance and properties ofthe compound did not change. Magnesium R-(+)-α-lipoate was a lightyellow powder throughout the storage period and showed no visible signsof polymerization or degradation. Chemical analyses indicated that itschemical composition, purity, and chiral purity did not change duringstorage under these conditions. In contrast, storage of R-(+)-α-lipoicacid under these conditions resulted in clumping of the compound,development of a strong sulfur odor, and formation of small and visiblegummy balls of dark yellow material characteristic of polylipoatedegradation products.

EXAMPLE 3 Bioavailability of Magnesium R-(+)-Alpha-Lipoate of thisInvention

The percentage of bioavailable magnesium was determined as thepercentage of phosphorous bound from a solution of phosphate.

Materials. Materials other than magnesium R-(+)-α-lipoate were obtainedfrom commercial suppliers (e.g., Sigma Aldrich Chemical Co., Inc., VWR,Alfa Aesar Chemical Co., Jost Chemical Co.).

Methods. The following procedure was employed. Experiments werecompleted in triplicate in which 1.43 g of NaH₂PO₄.H₂O (329 mg ofelemental phosphorus) was dissolved in 570 mL of deionized water. Thetest or control compound was dissolved in deionized water to a volume of30 mL. The resulting solution was added to the phosphorus solution togive a final volume of 600 mL. For each study, the phosphorus solutionswere titrated by addition of concentrated HCl or NaOH to five differentinitial pH levels: 4, 5, 6, 7, and 8. (These values of pH span the pHrange of the gastrointestinal tract.) Then the beakers containing thesolutions were covered with plastic wrap and placed in a shaker bath at37° C., shaking at ˜20 cycles per minute. This stirring rate has beenselected because in vitro antacid activity at such low stirring rateshas been reported to correlate well with in vivo antacid activity in thestomach. Samples for ion chromatographic assay of phosphate (Pi) weretaken just before titrations to the initial pH and at 1, 4 and 10 hpost-mixing; these later intervals have been reported to correspond tothe approximate residence time in stomach, the time available forabsorption in the small intestine, and the maximum time available forphosphorus binding that have been reported in related in vivo studies,respectively. The percentage decrease in phosphorus concentration fromthe original concentration in the phosphorus solution to that of thefiltrate represents the bioavailable magnesium in magnesiumR-(+)-α-lipoate (Mg RALA).

The experimental data (FIG. 1) demonstrate that the magnesium ion ofmagnesium R-(+)-α-lipoate is bioavailable in all parts of thegastrointestinal tract. Although magnesium R-(+)-α-lipoate has nosignificant solubility in this pH range, experimental data show thatthis magnesium salt dissociates sufficiently to provide 82% to 100% ofthe available magnesium throughout the pH range 4-8.

All mentioned references are incorporated by reference as if herewritten. When introducing elements of the present invention or thepreferred embodiment(s) thereof, the articles “a”, “an”, “the” and“said” are intended to mean that there are one or more of the elements.The terms “comprising”, “including” and “having” are intended to beinclusive and mean that there may be additional elements other than thelisted elements.

Without further elaboration, it is believed that one skilled in the artcan, using the preceding description, utilize the present invention toits fullest extent. The specific embodiments are, therefore, to beconstrued as merely illustrative, and not limitative of the remainder ofthe disclosure in any way whatsoever.

1. An oral nutritional and therapeutic composition, comprising a unit dosage or serving mixture of from about 5 milligrams to about 100 milligrams magnesium, on an elemental basis, in the form of pharmaceutical quality magnesium R-(+)-alpha-lipoate having greater than 95% purity and greater than 95% chiral purity.
 2. A method of promoting the assimilation of blood sugar in human tissues, comprising administering to a human, by mouth, a safe and effective amount of pharmaceutical quality magnesium R-(+)-alpha-lipoate having greater than 95% purity and greater than 95% chiral purity.
 3. A method of preventing or treating sequelae, complications, and co-morbidities of a metabolic disorder related to impaired mitochondrial glycolysis in a human, comprising administering to said human a safe and effective amount of magnesium R-(+)-alpha-lipoate having greater than 95% purity and greater than 95% chiral purity.
 4. A method of preventing or treating insulin resistance in a mammal, comprising administering to said mammal a safe and effective amount of magnesium R-(+)-alpha-lipoate having greater than 95% purity and greater than 95% chiral purity. 